Noninvasive physiologic pressure measurement

Abstract

An instrument for at least estimating physiologic pressure such as central venous pressure (CVP) non-invasively includes an ultrasound probe coupled to a display that shows the deformation of a vein as pressure is applied outside the body through the skin and soft tissues. A pressure transducer is applied to the skin to compress a vein, and an indicator coupled to the transducer shows the amount of pressure being applied when the ultrasound probe shows that the vein has collapsed. In the preferred embodiment, the transducer is an inelastic balloon filled with a liquid such as water, and the indicator is in fluid communication with the balloon. The indicator may be a mechanical gauge or meter, or may include a material that converts applied pressure to an electrical signal, in which case the electrical signal may be interfaced to a numerical readout. At least the probe and the transducer are preferably disposed in a hand-held housing.

1 . An instrument for estimating physiologic pressure non-invasively, comprising: 
 an ultrasound probe coupled to a display that shows the deformation of a body organ or vessel as pressure is applied thereto;    a pressure transducer configured to apply pressure to the organ or vessel; and    an indicator coupled to the transducer showing the amount of pressure being applied when the ultrasound probe shows that the organ or vessel has collapsed or become compressed to a predetermined level.    
   
   
       2 . The instrument of  claim 1 , wherein: 
 the transducer is an inelastic balloon filled with a gas or liquid; and    the indicator is in fluid communication with the balloon.    
   
   
       3 . The instrument of  claim 2 , wherein the indicator is a mechanical gauge or meter.  
   
   
       4 . The instrument of  claim 2 , wherein: 
 the indicator includes a material that converts applied pressure to an electrical signal; and    the electrical signal is interfaced to a numerical readout.    
   
   
       5 . The instrument of  claim 1 , wherein: 
 the transducer is composed of a material that converts applied pressure to an electrical signal; and    the electrical signal is interfaced to a numerical readout.    
   
   
       6 . The instrument of  claim 1 , wherein at least the probe and the transducer are disposed in a hand-held housing.  
   
   
       7 . The instrument of  claim 1 , wherein: 
 the ultrasound probe has a distal end; and    the pressure transducer is supported between the distal end of the probe and the skin.    
   
   
       8 . A method of non-invasively estimating central venous pressure (CVP), comprising the steps of: 
 applying pressure to a vein outside the body through the skin;    monitoring the compression of the vein using ultrasound; and    using the pressure at the point when the vein collapses as an estimate of central venous pressure.